Wireless Power Pitched as Replacement for EV Batteries

Stanford University researchers believe they've found a better way to build a long-range electric car. Amazingly, their solution has nothing to do with batteries.

By using resonating metal coils to wirelessly transmit large amounts of current between roadways and vehicles, the researchers say it's now possible for an electric car to have virtually limitless range.

Using magnetic resonance coupling, coils in the roadway could wirelessly transmit power to electric cars cruising down the highway. (Source: Stanford University)

"The idea is that the energy transfer would take care of the base load that you would need to propel the car," Sven Beiker, executive director of the Center for Automotive Research at Stanford (CARS), told us. "If you do the math, you see that it would provide enough energy for the car to cruise down the road at about 65mph."

CARS's idea is to use a concept called magnetic resonance coupling to transfer the energy. A resonating coil in the roadway would be connected to an electric current, which would generate a magnetic field, causing a coil on board a passing vehicle to resonate at the same frequency. With the two coils coupled by this magnetic resonance, electrical energy could be transferred between them.

The technology is new, but not unique. Researchers at MIT have developed a similar technology, and a spin-off company called WiTricity is aimed at wireless transfer of power to stationary devices.

Stanford, however, suggests that it can be employed with moving vehicles. Researchers say they can wirelessly transfer 10kW of power to a moving car across a distance of 6.5ft. It's not known yet how many of the coils would be needed or how far apart they would be spaced in order to power a car driving down the highway.

"It could be 10ft or 20ft or 50ft," Beiker said. "More research will tell us what the exact number is."

Better solution, maybe. And while I have to applaud any and all efforts to explore alterative fuel technologies, the key downside to this, as it strikes me, is that the whole thing is a moot point unless there is significant buy-in and commitment to alloting huge budgetary resources to building out new infrastructure. Already, cities and states are struggling with how to finance the upgrade of aging highway systems and bridges. Unless something like this could be bundled as part of a nationwide road and highway upgrade plan, I don't see how any private investment could facilitate. Finally, again at the risk of being a naysayer, good luck getting something like this to gain any kind of traction in this divided government.

This might be something we see in a hundred years, but looking more short term. Why not just put powered rails in the road. That kills two birds with one stone. If you are on rails, you don't need to steer.

The Panama Canal— the largest construction project in history at the time— cost $375 million in 1913 dollars. The CPI from that time to today has grown 21.2X, making the cost in 2008 dollars about 7.95 billion dollars. So $800 billion today would buy from scratch, 100 Panama Canals. This is approximately the Wall Street Bailout.

Here's another, perhaps more practical purchase–

The approximate cost of constructing a twin track 10,000 km maglev train system including 300 kph trains, tunnels, bridges and stations, between major US cities is about $800 billion. Average construction cost would be about $USD 50 million per kilometer. About 1200 maglev cars would be needed. The rolling stock would cost only US$20 billion.

So electric cars are fine, and I'll be a buyer someday. But let's build something amazing.

Grossly impractical implimentation of power transmission over a distance. It's a fine technology for cordless charging of cellular handsets, flashlights, wheel chairs, electric scooters, fork lifts, etc. But for highway use, its DOA.

What happens when a commuter rail line loses its catenary power? A thousand passengers are stranded, stuck. Now multiply this by tens of thousands on a major freeway when their vehicles grind to a halt. Get the picture?

Even electrified railroads have required alternative locomotion sources at times. I assume those batteryless cars will require some form of serious energy storage and a capacitor bank will be insufficient.

It is very common in electrified rail systems to have gaps between power distribution sources, third rail or catenary gaps to isolate segments. As long as some of the self propelled cars in a train are not within the gap they will be able to re-start and move along. Now, picture bumper to bumper traffic. What if you are stopped between charging coils long enough for the capacitor to run out of charge? Even if you envision autonomous self driving vehicles controlled by the highway so that traffic jams or accidents will no longer be issues, you still have unforeseen events that could dynamite traffic flow. For example vehicle breakdown, or a sudden change in the weather, or a wild fire, or vandalism.

Who finds and posts these sophomoric ideas? I'm begining to think that DesignNews is a hack site for the green agenda. If this is truly mainstream engineering thought, this country, and world for that matter, is in more trouble than I thought.

Seriously? designing a roadway like a kids toy slot car track to get power run the electric cars? What happens when I want to pull off the road or go where the power isn't?

In 4 pages of posts there are a litany of reasons which I'm sure were generated in less than 5 minutes of reading this pipe dream article of why this is a poor idea.

I know... maybe we can subsidize electric roads the same way we're subsidizing electric cars. Yeah! Great plan!

I'd sure like to know who funded development of this idea. I hope it wasn't us tax-payers. A total waste of resources. A high-school freshman could tell you this couldn't possible become a reality because of the multitude of negatives.

I wonder what would happen if I walked across the road with my pace-maker.

Isn't the U.S. Navy developing a magnetic induction launch system for aircraft carriers to replace the 'old-tech' steam system ?

Years ago I saw AGV's in an auto plant. At each 'wait' point there was a charging station. Disney World has a monorail - not the fancy Mag-Lev, but at the time it was a showpiece. This concept may not be ready for the 'big-time', but just as certain cities have light rail and subways, the first step may be a public transit application. I don't know if it can be cost-effective vs. the catenary electic.

The internal combustion engine was at one time referred to as the infernal combustion engine. It helped solve the pollution problem of the emissions of the horse-drawn carriage. The future is hard to predict.

Exactly right! The hot swap of battery packs was talked about over decade ago and is now resurfacing.

The problem is the infrastructure cost. The cost to just install it would be monumental. The cost to maintain it unacceptable.

A great example is electrification of the railroads. This started during the steam era. Then diesel electrics came along. No catenaries to maintain. The overhead wires have all but dissiapeared except where the density might justify it.

In addition, what do you do during the transition to such a system? What is the advantage of a car? You can go lots of places not served by systems like trains and other mass transit. So, you will still need batteries or a gasoline engine.

When you lay it out like that, the plan appears even more daunting and long term. While many of the best solutions to our hard problems will be years, maybe even decades, down the road, we have to focus on a mix of short-term and long-term remedies. It's easy to shoot something down like this because it seems impossible to get off the ground and with no real benefits to be seen in the short term.

Wow. Great story, Chuck. If we were able to create the intercontinental railroad and the interstate system, we could do this. It would be a trick to distribute the ongoing electrical costs to individual vehicle owners. Perhaps toll booths would be the solution. It would be interesting to compare energy costs against battery-powered cars, or even gas powered cars.

I wonder if the magnetic field could also prevent cars from hitting each other. That would deliver huge savings in life and property damage.

@Beth,I agree with you completely. It's a nice thought but it will never happen. The main reason? Money. This paragraph caught my eye:

"To make it all happen, every "powered roadway" would need a very heavy cable running alongside it to carry huge the amounts of current needed for long stretches of roadway. "

Number one: Heavy cabling? You realize that we are on the downward slope of most of the natural resources on this planet. Copper used to be real easy to mine. Dig a hole, follow the seam. The low-hanging fruit is gone now. Copper prices have skyrocketed in the last 10 years.

Number two: Huge amounts of current. Here we are, back to electricity generation again. Just exactly how much electricity does it take to move a car down the road one mile with this system?

Cute idea, but we should really be investing in conventional rail, not high-speed. Just get trains running from one city to another on-time.

You could have the car's electric coil metered to measure the amount of charge gathered from the roadway. The cars could then transmit the data to a billing center.

The roadway providers would have to find a way to split that up equitably. GPS could also be used to determine which roadways the car used and for how long if different utilities provided for different sections.

This articles states a glaring contradiction. 1) If you do the math, you see that it would provide enough energy for the car to cruise down the road at about 65mph." VERSUS 2)It's not known yet how many of the coils would be needed or how far apart they would be spaced in order to power a car driving down the highway."It could be 10ft or 20ft or 50ft," Beiker said. "More research will tell us what the exact number is." Did Beiker really do the math?

What about the efficiency of the system? With the push towards higher efficiencies in vehicles, will technology be competitive and meet regulatory efficiency requirements? I suspect that overcoming the energy losses in the system will be a major challenge regardless of the economics of other aspects of the system.

Similar to the EV arguments regarding range - how practical is it to have a car that can only use a limited set of roadways?Not too many consumers can afford to buy a car for limited use.Granted, a hybrid version of this could allow for operation away from the electrified roads and still reap the weight benefits.

I would also like to see the power requirements to keep a highway running at speed.I haven't put pencil to paper, but I would suspect that as the number of coiled cars on the highway grows, the less energy will be available, and everything will slow to a crawl.With adequate power this might not be a problem since the speed of traffic is usually inversely proportional to the number of cars on the road anyway.

I almost want to say that fleet vehicles that run set routes would be a good place to start.If the cost was right, this would alleviate the fuel logistics costs of a fleet.But to keep costs affordable it may require widespread adoption to repay the capital of building the roadways.

This is a neat idea, but it's not going to be practical for years. It suffers from the chicken and egg problem. Do you build cars that can use it first or do you build the infrastructure first. (note the E85 cars we have now - most of them can't get E85)

Since we are contemplating changing the infrastructure, why don't we look at what we could do now? By making parking lot spaces "pull throug" we wouldn't be wasting gas backing cars up. By making all the traffic lights "smart" lights (which could be done with cameras) you would eliminate millions of wasted gallons of fuel caused by cars idling at uneccesary stops as well as the gas needed to bring them back up to speed after that stop. And these changes would act on every car in the system now - not just special electric cars.

These are changes that our government could cram down our throat that would actually help everyone.

Any genius can come up with solutions to problems as long as they don't have to pay for them. How many of us have thought "what if" -- and then realized the biggest obstacle is not the technology but the money. Even the Stanford brains admit they can't figure out how to fund this obviously wallet-emptying idea. Meh. [Edited: Speaking of brains, even I got it wrong. I originally had said MIT when it is Stanford. Must be catching.]

This has been floated round since Tesla's day, and except for niche applications (induction heating) it doesn't pass the back of the envelope calculation test. We'll see all-electric railroads here sooner.

Let's just wire the roads in sections, say 5 miles of the HOV lane. Use that juice to power the vehicle or recharge onboard batteries. Have "toll booths" every so often where drivers can swipe their cards to pay for amount of charge used. You wouldn't have to tear up thousands of miles of road, just cut a groove & lay the "wire". No this won't be for everybody but it makes the switch to electrics much more attractive.

The problem with hot swaps is there is no battery pack standard & nobody seems to address that.

Someone had better figure out the efficiency of the energy transfer between the road coil and the coil in the car. That is a big air gap. This is nothing more then a transformer with one coil in the road and one in the car. The air gap is huge unless you want to reduce the vehicle ground clearance. Transformers are very inefficient with large air gaps. The next technical issue to consider is what operating frequency will this be? We will to be transmitting at that frequency and interfering with everything in the area.

Now let's look at the car. A car made mostly of steel and we drive it over a magnetic field in the road. The magnetic field will attract the steel pulling the car down making it appear much heavier to the tires. That adds friction slowing the car down. Oh and don't forget the magnetic field will be pulling the car towards it as the car approaches. Then pulling the car back as the car trys to move away form the coil in the road. Could make for a jerky ride. We better do more homework before applying to the government to fund this research. Where are the professors at Stanford that should be getting these questions answered? We need a reality check with basic physics here.

Read the link to Witricity for more information on the energy transfer method. It is not typical transformer coupling. It accomplishes energy transfers over much larger distances than transformer coupling, apparently up to several meters, and apparently without the forces that would be associated with typical transformer coupling. Perhaps without the interference from steel as well.

That doesn't mean that this idea is feasible, but it has been thought through a little farther than transformer coupling.

I can think of a lot of ways that this type of idea could be incrementally implemented in ways that might make sense. When you are taling about battery costs in the range of 10's of thousands per vehicle, there is quite a revenue stream if battery powered cars really are the future. The resources required to make batteries on a scale required to replace millions of gas powered vehicles may prove to be a daunting task that gets more and more expensive over time.

It strikes me that with school boards starting to ban WiFi in classrooms because of their percption of the dangers of microwatt electromagnetic fields, I don't understand how 10KW fields could ever be approved or accepted by the general population.

There is no mention of the resonant frequency of this system but, as Eddycurrent implies, it seems that any magnetic material in range (resonant or not) could get pretty warm. My induction cooktop works really well.

This whole idea just strikes me as something that is just so impractical it will never get past third base. Plus it is certainly not new. Add all the other reasons that the other commentators have pointed out:

#1) where in the heck are you going to get the infrastructure to provide the 'power distribution' points along a highway (every 50 ft!).

#2) the efficiency problem

#3) the huge fields involved

I could go on and on. This idea is, at this point, really half-baked. Somebody had to be desperate to even publicize this. Silly and stupid both.

I agree with BobGroh and others - this is a half baked idea that is easily proven impractical in 5 minutes of honest thinking. This scheme works OK for trains and trolleys and monorails at Disneyland - but not for an entire transportation system.

I think we (in the technical community) need to all take a deep breath and ask the deeper question: "what problem are we really trying to solve?" and "what's the best way to get there?".

Electric cars, with batteries or even with "slot-car drive" do not solve our energy problem. They do not use less energy overall (about the same) and only serve to transfer the energy source from Oil to Coal + Natural Gas + misc. Until the "misc" power sources of the grid are a majority renewable, EV's do not help much at all. They are just a big distraction and wasted cost. Let's focus our efforts to convert the grid to renewables, which will require adding energy storage on the grid, and let the automotive sector get off of fossil fuels more directly.

Here's a much more practical near-term solution: Coal-to-Gasoline http://www.ultracleanfuels.com/ China, India, and other countries have already discovered this...but the USA is still pouring government money down the proverbial rathole of EV's. Cut out the "middle man" (of power plants burning coal) and just make gas from coal!

Longer-term solution is Biofuels or Solar Synthesized fuels, to get us off of all fossil fuels.

Note that either of these requires ZERO (or minimal) change to existing infastructure, and still accomplishes getting us off of oil (near term) and fossil fuels in general (longer term).

Just deploying such a system across the US interstate highway system would be one of the largest single infrastructure undertakings I can imagine. If deployed within cities, I wonder about unintended effects of high flux fields. If only we had the national will to do MagLev passenger trains. That would be a much more limited undertaking and meets the definition of "mass transit." My choice would also be to build more light rail for commuters first.

I'm not too sure how wide spread this system is supposed to be. If the coils are to be made of copper, that's a lot of copper. It's hard enough to keep the roads in good enough shape that motorists don't loose tires from chuck holes. Keeping an electrical system going with the freezing, thawing, truck traffic, and corrosive chemicals being dumped on the road, would be a monumental challenge. Access to the buried coils would be a problem. As I always say, you go first.

People steal everything. Some moron will dig up these lines in the middle of nowhere and steal them. True a few will get fried, but it hasn't stoped them from trying it in substations. These are NOT rational people. You will also have the indoor grower of less than legal substances stealing the power as it goes by the grow room simply by parking a car on the side of the road. True a BIT more complicated than that but not a lot. Most of these people aren't to bright, but in mass they have some very innovative people and theft will be wide spread!

I think it would make more sense to redesign cars and roadways so they work together like the steel ball and bumpers in a pinball machine. You'd crash your car into a convenient bumper, and it would fling you back into the roadway with a high-g pulse of acceleration. Municipalities could even install "flippers" which would allow them to "gunch" vehicles into different roadways -- or even off the road all together!

My math indicates that this is an altogether feasible approach, in both energy and economic terms.

Given the large number of people with implanted medical devices with wireless interfaces, I can imagine the dangers posed by ubiquitous high EM fields capable of frying the sensitive electronic circuits used in such devices.

Given the large number of people with implanted medical devices with wireless interfaces, I can imagine the dangers posed by ubiquitous high EM fields capable of frying the sensitive electronic circuits used in such devices.

I posted a comment to a Design News article several months ago outlining inductive power for vehicles!

Set that aside. Not important (well, not to the rest of you at least). I'm going to take issue with the "not dangerous portion". We're talking about a coil running at high frequencies. Wouldn't any metal coming within this range have currents induced in it? And heat up? I've given practical demonstrations of inductive heating to salesmen. I have them hold a 1" washer tightly in their fist, holding their fist over the inductive coil of a 350W system. Non-contact heating surprised them, as well as how fast it worked.

A typical mid-sized auto takes around 20KW to cruise at 60 mph. Let's assume that the highway is busy, then cars might be spaced out every 50 yards or so. That would be about 35 cars per mile. The efficiency for transfer of energy done by the original work at MIT was around 40% in a lab environment. Let's take the optimistic assumption that we could achieve that in the real world with a moving vehicle. Each vehicle would require 50KW just to maintain speed, and even more if we were expecting to recharge batteries as well. The total energy requirements per mile would be about 1.75 Megawatts. Every 10 miles of road would require a mid-sized electrical substaion, and of course the additional high voltage 3 phase power lines. The best estimates that I have read to date indicate that the nation would have to quadruple its existing generating capacity to electrify the nations transportation industry. There is simply not enough wind or solar to do this, even if we were to extract 100% of what is available.

All too often such ideas tend to ignore the incredible energy density of gasoline or diesel fuel. Useful alternative transportation means should not not ignore basic physics!

Mark S Happy to see you read some Tesla! Truly a man before his time yet this genious was blocked by the likes of J.P. Morgan and other Wall St. types. Please rememberHE DID HAVE an ELECTRIC POWERED Pierce Arrow THAT DID NOT USE BATTERIES FOR IT'S ENERGY SOURCE.As the EV thinking moves closer to engineering laws of physics and quantum physics the old masters predictions WILL be proven correct.

Something else that is interesting and discusting to me are the comments from some "engineers" made on these pages which, are disturbing to me in that they are destructive and detramental rather than objectively critical and creative. To me, and I believe other engineering professionals, this does NOT present to the public a true picture of our profession, and I hope to see gone from DN etc. ASAP.

... of most design reviews and FMEAs I've attended -- where every engineer in the room wants to show how smart he is by DEFEATING an idea rather than selflessly improving the idea. I concede that this story fits better in Popular Science or Popular Mechanics rather than an engineering periodical. (I'm suspecting it's a slow news day; engineering periodicals need to fill column-inches, too.) The challenge is to show how smart you are not by knocking this idea, but rather by taking some small portion of the idea and leapfroging into something better. Then, post your idea here and we'll all show you how smart we are by knocking it endlessly. Cheers!

Practical Engineer, I understand where you are coming from, but it is a major part of the role of an engineer to determine feasibility of an idea.

In this case, the title promises the replacement of EV batteries.This is only practical if you electrify every mile of road in the country.The cost and time involved mitigate against that.There have been many proposed alternatives to the ICE, but none of them are gaining a lot of traction.Counting all the hybrids and electric vehicles that have been sold (Prius, Volt, Leaf, Tesla) you have a very small percentage of the vehicles on the road using electric technology of some sort.And most of them are going to be hybrids that still use an ICE.So, the impact is negligible.

Now, if you relax one of the goals, that of replacing batteries, you might have something workable.Assume that vehicles have batteries.Electrify the long distance roads and let the vehicles charge from the roadway and you might have something.Of course, you still have a battery.Another alternative is to have an ICE for short haul situations, or situations where the electrified roadway is not available yet.This might start to be useful.

As of now, there are no technologies that are practical for powering personal vehicles other that the ICE (I include hybrids which use and ICE).Any replacement would have to provide the same utility at a similar price to be voluntarily adopted.Personally, when I can I use public transport.

Amen to the Practical engineer- I give you 5 stars.My favorite line: "every engineer in the room wants to show how smart he is by DEFEATING an idea " –-- you have an outsiders view of design engineers in general. We are all guilty in that manner, and we all routinely say, "It'll never work".Accordingly, there are 4 pages of comments here which are (mostly) accurate and real roadblocks to this idea, and I applaud them all; because largely, this IS a silly idea .... But ONE thought kept coming back to me again and again:In 1975 there was a proposed technology that had a very similar audience.It required the PREPOSTEROUS idea of building out a nationwide cellular infrastructure!(Ludicrous-! ! )37 years later there are so many networks, several do not even cross-link [i.e., cdma/gsm].

I bet the current presidential administration would love this idea, because it would get votes from folks who don't understand the issues.

Personal, powerful, adaptable transportation. That's the automobile, and it's been the 'American way' for about a century. The ICE equipped car goes where I want, when I want. Hybrids are the same. Change to EV and I lose some flexibility about where and when, since I have to adapt schedule to vehicle range and charging requirements - more planning required. Further restricting me would be a car coupled to a particular kind of roadway, which lets me go when I want, but takes away more flexibility about where, since we will likely not power roadways within 'small battery' distance of every location my ICE powered car can go now. If I were building massive transportation infrastructure that would provide "almost when I want, but not always everywhere I want" solutions, I'd want my money on mass transit, not resonant coil highways. Given our current political reluctance to accept even modest tax increases to sustain the existing road infrastructure (Federal gas tax is same 18 cents/gallon as in 1993), I can't say I have much hope for any new transportation systems.

That said, some of the arguments in the comments here both for and against seem built on questionabe values and conversion factors. For example, 20kW to maintain 60 mph would be 20 kw-H for 60 miles, or a total of 1200 kw-H for a 60 mile trip at 60 mph. Gross heating val;ue of gasoline is only about 125,000 Btu/gal, or about 36 kwH/US gal. Using that gross heating value and 100% efficiency (neither of which are reasonable assumptions), it would take 33 gallons of gas to go 60 miles using the stated 20 kW power requirement. By some miracle, my small pick-up truck only takes about 3 gallons for that distance.

I had similar questions about the math around the Panama Canal comparison.

Personal transportation is a hot-button issue with lots of folks. Careless use of figures and conversion factors doesn't help the already charged conversations. Since we tend to think of electrical power in kW and liquid fuel consumption in mpg (in the US), it's worth taking the time to run some reasonableness tests before citing claims about how cheap or costly a particular system might be.

richgtoc, I think your math is wrong. 20kw for 60 minutes is 20kwh. In those 60 minutes you would travel 60 miles, so the total would be 20kwh for the 1 hour, 60 mile drive, not 1200kwh.

p.s. information on Tesla motors' site makes the 20kw look pretty believable. They claim to be at about 250 Watt Hours (per mile) at 60 mph, which is a bit lower than 20kw, but their drag coefficient is lower than average.

Thanks for catching me on exactly what I was criticizing others for. We pay the price every day for our use of mixed measurement systems. Ouch. Mea culpa. The result looks much more reasonable at 20 kwH.

In the old days, I would have put this down on paper with the units and checked the unit conversions and found my error. Even though I put the units to the side of the cell entries in Excel for this exercise, the entries weren't in a form that forced me to do a complete units check.

The first question that I see is about the efficiency of the energy transfer. That will be the very most limiting portion of the system as far as the technical challenges go. The second challenge will be much bigger, which is figuring out how to pay for a roadway that can transfer power to the vehicles. That sort of infrastructure is not cheap, it would cost a whole lot more than good concrete roadways, which appear to be beyond the scope of possibility in this part of Michigan.

Of course, the efficiency can be a whole lot better if power is only transmitted when there is a vehicle to recover it. That sort of control system can certainly be built, but it will not be cheap either. So now we have two parts of the system that each are quite expensive, and what has not yet been mentioned is how the accounting for the energy delivered will be billed to the user. So while the concept is indeed quite exciting, it certainly looks like one of those non-affordable projects, not because we can't design it, but because we can't afford to pay for it.

One other serious concern is about where all of this power would come from. The problem would be the worst when a whole lot of folks were driving on the same road at the same time. The logistics of bringing a whole lot of power to the roadway at certain times is another area that be expensive.

Of course some will say that it is easy to shoot down an idea, and they point to the cell phone explosion of 15 years ago. The differences are that cell phone infrastructure is a lot cheaper, and more importantly, the cell phone infrastructure could grow from the revenues as time went by. And there was no competing technology to provide a cheaper alternative. Inductive power transmission does not have that advantage, present cars and gas stations are very effective at providing comfortable transportation. So that is a big difference.

You could have the car's electric coil metered to measure the amount of charge gathered from the roadway. The cars could then transmit the data to a billing center.

The roadway providers would have to find a way to split that up equitably. GPS could also be used to determine which roadways the car used and for how long if different utilities provided for different sections.

... remember Heinlein's "The Roads Must Roll" or Asimov's "Caves of Steel"? Active mass-transit roadbeds, whether megascale conveyor belts, or electrically wired, wireless, microwave, maglev, bla bla bla, will always be horrendously expensive and prone to breakdown and (these days) fundamentalist or greenie terrorist sabotage. High-density internal energy storage and freely-driven vehicles are the high standard that's been set; anything centralized will be a step down into tyranny.

Unlike 99.9% of the readers here, I actually did some R&D work in the late '80s with resonant power couplers for commercial aircraft applications. Inefficient and unreliable for starters. At 10kW power densities, even with 25-year more mature power devices & embedded control, you're talking a huge waste in power and probably MTBF of months, not decades.

IMO it's time to cast away altogether the bright idea of mass transit except in very dense urban zones.

Yes, I agree that even the best resonant coupling will not be so very efficient. I have observed the other writeups and they either ignor efficiency completely, or they express power transfer in terms that I find non-informative. It becomes clear that there is something to hide. At least I see it that way. Your assertion tends to verify what I have been observing. Thanks for the input.

Okay, maybe I'm a bit short in my critique because I'm generally annoyed with the initial premise here, that's hiding in the background that no one is talking about which is:

Why are we thinking of this in the first place?

Why are we talking about the idea of electric vehicles to begin with? The ICE has been a steady workhorse for man for about a century in various forms. It does the job, cheapy effectively, and by most people's account, efficiently.

So what's all this about? Getting away from fossil fuel? Why? Well, someone thinks that the ICE is bad for the environment and causes global warming/cooling/change/weather... whatever the name of the day is.

The whole premise of this exercise is to do something that when looked at through the lenses of overall efficiency, cost effectiveness, reliability, and total environmental damage makes absolutely no sense what.so.ever.

It is never a bad thing to consider alternatives, or revisit ideas as new technology becomes available. But there does come a point where pouring good money after bad, to sway public opinion, support faltering businesses that can't compete with the legacy technology, is just a really dumb idea.

And to those who are complaining about those of us who are 'quick to tear apart' ideas vs. build them up, I'd submit to you that we just come to the conclusion above faster than you did, and are ashamed that more professionals aren't as astute. (Truth be told however, it would appear that reality is winning out over fantasy in the end.)

Okay, maybe I'm a bit short in my critique because I'm generally annoyed with the initial premise here, that's hiding in the background that no one is talking about which is:

Why are we thinking of this in the first place?

------------ Because we keep spending trillions to overseas oil dictators and terrorists in military/yr, Persian Gulf/OIl wars and balance of payments costs. Now we know the cost of oil, other FF will rise so the smart thing is get off the train before it wrecks. My EV takes so little energy it isn't noticable on my $24-45 Electric bill. So I do EV's for cost, sercurity of my fuel source I can make myself cheaply and to be patriotic and keeps us out of future oil wars. Or do you like the 6k US soldiers dead, etc for international oil companies? But other than that, no reason.

Why are we talking about the idea of electric vehicles to begin with? The ICE has been a steady workhorse for man for about a century in various forms. It does the job, cheapy effectively, and by most people's account, efficiently.

----------- Depends on what you call cheaply. 20% of your tax bill directly subsidies oil companies. Real cost of oil is another $2-3/gal. And sorry but eff is not one of oil. EV's are 3-6x's as eff. But even strait up, KIS well designed EV's can be far cheaper using lead batteries and forklift tech and still get 100 mile range as the EV-1 did on lead.

So what's all this about? Getting away from fossil fuel? Why? Well, someone thinks that the ICE is bad for the environment and causes global warming/cooling/change/weather... whatever the name of the day is.

------------ Go down and read the numbers on the gas pumps. Add up all you spent on gas last yr. Now double that in 2-3 yrs.

The whole premise of this exercise is to do something that when looked at through the lenses of overall efficiency, cost effectiveness, reliability, and total environmental damage makes absolutely no sense what.so.ever.

----------- As done it doesn't and not likely ever to be used by cars but third rails for semi's, buses could be good. Since a fueled gen only takes 30-60lbs to give an EV unlimited range at about 100mpg, YMMV, it makes little sense using more than 100 mile batt range in most cases. Remember the EV-1 charged like this and when it caught fire a couple times because it's not a good system, they used that as an excuse to crush them. None of this is new and used over 100 yrs and very limited.

------------ Best way to do it is have some PMagnets on a trolly under the EV or even ICE car, semi and coils in the road pull it along making a linear motor. Keep the gap under 1" and it's eff.

It is never a bad thing to consider alternatives, or revisit ideas as new technology becomes available. But there does come a point where pouring good money after bad, to sway public opinion, support faltering businesses that can't compete with the legacy technology, is just a really dumb idea.

And to those who are complaining about those of us who are 'quick to tear apart' ideas vs. build them up, I'd submit to you that we just come to the conclusion above faster than you did, and are ashamed that more professionals aren't as astute. (Truth be told however, it would appear that reality is winning out over fantasy in the end.)

-------------- We have been driving EV's for decades quite well thank you. google EV Clubs or EV racing and you might find out what the world is missing.

----------So think about the next time you fill up that instead of $40 in a similar EV you'd spend only $4 plus save the time, hassle of gas station stops. That's it, $4, now $10, now $50 1-5x's/week and soon it adds up to real money. Mine stays in the bank for other better things. So keep up the good work supporting oil companies, dictators and terrorists.

Wow... There's an old adage, "I can explain it to you, but I can't understand it for you." I think that's very apropos now.

Touting the talking points from your favorite greenie website isn't going to help you amongst the thinking crowd. You conveniently neglected to cover real costs to implement, and real environmental damage from all the components made from 'unobtanium' that will be/are necessary to make these systems work to the levels you expect.

No I don't want to see 6k dead soldiers, a few of which were friends of mine, and I lost 343 brothers and sisters on 9/11 so put that card back in the deck. We didn't ask for 9/11 and I don't agree with our response. We shouldn't be playing nice war like we did in Viet Nam, we should go scorched earth so the people that respect only force recognize, we have it, and will use it again. These methods don't work well for training pets, children or dictators, and the state of the world today proves this.

But veering off the path to reason, I somewhat agree, we shouldn't be getting our oil from the middle eastern nut jobs... so, why then can't we develop our own? That's right... we're going to FORCE everyone into impractical EVs by making the cost of fuel whether it's subsidized or not (um... just like the Volt) so expensive they'll HAVE to go to the new alternate technology.

So Chevron isn't allowed to engage in energy storage or management of any kind other than fossil fuels? Is that what you're driving at? (I know full well you're insinuating that they are evil and are trying to drive up the costs to further their pig-ish capitalistic goals). Well, by that logic, who should be allowed to have those patents? GE? Wait... they don't pay taxes, that won't work... How about Solyndra? Oh... they went out of business... dang it...

Fact is Chevron, which is one of many companies in the energy business, is looking at ALL FORMS of energy. Be it fossil fuel, bio, electricity, whatever if they plan to be around the next 50 years, they better have a handle on what's up and coming.

Besides that, NiMH is dead... Li+ is the way to go... unfortunately neither of which are good for the environment to produce or dispose of. A bit of an inconvenience there for saving mother earth, which after all, is the big picture here, don't kid yourself or anyone else here.

If EV is so fantastic, why are developing nations still working from ICE? They may be including some EV, and for commuter routes that's probably a good idea, but for any non-programed independent route that needs to be taken, you just can't extend the extension cord long enough and put in enough plugs. If EV is the way to go, all the new roads, and infrastructure should be being built from the ground up, when it's most cost effective, not 50-75 years after the road has been in service. Unless of course, it's not really all that feasible in the end.

EV racing... yeah, I think I saw that on Speed. Oh.. never mind that was a top fuel dragster. For the amount of subsidization your EV has received, and continues to receive, You're investing (well, not you, the tax payers) a lot more money behind the scenes from the final sale price, to all the components tied into the design from start to finish.

So, I'll keep supporting the gas companies, and I'll push for utilization of our own resources here in the states and tell the dictators to go pound sand wherever they please to put it. You hug your pillow tight tonight and stick with the 99% crowd, they can use another good spokesperson.

A vehicle at highway speed easily needs 10kW, more likely 15-20kW of motor power. If we assume 10kW, that means this feigned mystery of how many coils is easy...it's CONTINUOUS for the full travel distance of a car. If it's 20kW, one coil the full length of a car won't cut it, so now you need to pull a trailer. So, rather than all the heat, EM radiation produced by inefficient induction coupling (resonant or otherwise), we actually use a TON (literally more than that) less copper by using overhead trolley wires (or embedded slot car style power rails). How did I figure all this out? I didn't go to, or get a cushy academic job professing impracticality at, Stanford, I guess.

Once again there seems to be less attention to the efficiency of the transfer. Really good transformers carefully built on a low loss core achieve up to 98%, if the coupling is good, and if everything is operated within the design specifications. BUT these really good transformers are not cheap.

Now what would the cost be to put a decent transformer into a mile of roadway? If it needs to transfer 10KW toa vehicle for that distance it is going to need to be "fairly big and heavy", and it will cost a fair amount. To avoid it being horribly inefficient it will need to switch on as the car enters each section and switch off as the car leaves. I designed a system like that for a maglev train quite a few years back, and while it was quite reliable and relatively simple, it would not be cheap. So now we would have a mile of quite expensive roadway, which may not last one winter with Michigan's road-salt application policy, And you have a very expensive mile of roadway. Of course to be of any real value there would need to be lots of miles of roadway. So that would be quite expensive already, with no power connections and no cars.

Next, where is all of the power for the roadway going to come from, and how will the data about who used how much at what time be recorded. This is important because it is only fair to charge those who use the energy for using it, similar to the way today we each pay for the gas that we put in our tanks. So now we add a fairly complex billing system to the price of the road. All this and still no discussion about the car and what it costs, nor any mention about the effect of all of these magnetic coupling fields on people in the area.

My point here is that just because it can be done does not mean that we can afford it. I yhave not mentioned the environmental concerns that others brought up, but they are valid also.

Has anyone stopped to consider the risk to health of 10-20kW of radiated energy magnetic or otherwise? I get a mild headache rather quickly using a mobile, and that's only ~5W. Crazy stuff. It's true Uni's aren't turning out much these days in terms of a braod understanding of the real world.

I may be wrong, but i feel this is an invention for the sake of invention. Implementing this will be a herculean task. There is no mention about the health hazards which i presume will be low in this case. But to be positive this is a brave attempt

I have been working with high efficiency transfer of magnetic energy over large air gaps for some time, and see two reasons why this might not be a wide range success for EV. This comes despite some successful demo projects. The magnetic transfer can be considered as a transformer with very large spread inductance. The spread inductance limits the possible transfer of energy. By use of resonance the spread inductance can be reduced,- but LARGE CURRENTS are circulating in the copper coils. This means high copper loss must be accepted or very big amounts of expensive copper must be used compared to a standard transformer of the same size.The transfer of power also increases proportional to drive frequency, but eddy current and proximity effect losses (and currently also slow IGBTs) are limiting how high it is possible to go in frequency. Very expensive copper wires of litz type can be use but the copper budget for a road will then be even much higher. Next comes the personnel danger. Under the car there must be mounted an efficient screen for the B-field, a ferromagnetic plate returning the field back down , and the field must only be left on for a short moment as long as the drive coil is safely under the car. This reduces the duty cycle for the energy transfer and further increases the transfer losses.Designs like this look very nice in a limited experiment, and scientists involved have a lot of fun playing with this without coming up with a viable solution for the public in my opinion.

I myself believe much more in an advanced very low weight carbon fiber based overhead dual-brush solution based on damm fast optimally controlled servos tracking overheead power lines at millisecond level,- thus a two wire electrical connection. The power line can be made as an "open" two-wire cable protected from rain/snow on the active underside.The bruch device is intelligent and pops up from the car and connects as soon as it observes such lines. Preferably operates at aronund 2-3kV so that it can drive a simple converter. The cars /trucks/busses must have some battery. The power lines are only needed on long straight parts of the roads. Thus this system will be much less expensive to build/maintain than the systems for traditional streetcars/trolleys.

Some cars are more reliable than others, but even the vehicles at the bottom of this year’s Consumer Reports reliability survey are vastly better than those of 20 years ago in the key areas of powertrain and hardware, experts said this week.

As it does every year, Consumers Union recently surveyed its members on the reliability of their vehicles. This year, it collected data on approximately 1.1 million cars and trucks, categorizing the members’ likes and dislikes, not only of their vehicles, but of the vehicle sub-systems, as well.

A few weeks ago, Ford Motor Co. quietly announced that it was rolling out a new wrinkle to the powerful safety feature called stability control, adding even more lifesaving potential to a technology that has already been very successful.

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